1. Field
This invention generally relates to the recombinant production of therapeutic proteins. More specifically, the invention is directed to glycosylated interleukin-2 muteins which can selectively activate T cells (PHA-blasts) and reduce activation of Natural Killer (xe2x80x9cNKxe2x80x9d) cells.
2. Background
The biological activity of a glycoprotein is dependent upon not only the integral structure of the protein, but also the properties of the oligosaccharide covalently attached to the protein. By influencing the physico-chemical and biological properties of proteins, oligosaccharides can modulate the therapeutic effect of a glycoprotein pharmaceutical. It is well recognized that glycosylation can affect solubility, resistance to proteolytic attack and thermal inactivation, quaternary structure, activity, targeting, antigenicity, functional activity, and half-life of the protein. The role of oligosaccharide in determining the in vivo activity of EPO and the half-life of tissue plasminogen activator has been reported.
Proleukin(copyright) (interleukin-2) has been approved by the FDA to treat melanoma and renal carcinoma. However, due to the toxic side effects associated with interleukin-2, there is a need for a less toxic IL-2 mutein that allows greater therapeutic use of this interleukin. Although non-glycosylated interleukin-2 has been produced in E. coli with full biological activity, proper refolding of the recovered protein and the potential for altered pharmacokinetics have been areas of concern. It is known that the purification of interleukin-2 derived from E. coil requires the use of chaotropic and toxic agents such as guanidine chloride and urea. Thus it would be advantageous to produce glycosylated IL-2 muteins in mammalian cells where the use of harsh reagents can be avoided.
U.S. Pat. No. 5,417,970 to Roskam et al. (May 23, 1995), incorporated herein by reference, discloses a wild type IL-2 preparation. The above-cited related application of Shanafelt et al. discloses IL-2 muteins and states that the muteins may be expressed in a variety of cells, including microbial, plant, and animal cells, including mammalian cells. We have now found a way to make such IL-2 muteins in glycosylated form from mammalian cells. The characterization and details for making a preferred IL-2 mutein are described below.
We have developed a method for the production of glycosylated IL-2 muteins from mammalian cells. Preferably the cell host is CHO cells, but the production can be done with other cell hosts including HKB (see U.S. patent application Ser. No. 09/209,920 to Cho filed Dec. 10, 1998, incorporated herein by reference), myeloma, and 293S cells. The production medium is preferably a chemically-defined medium free of plasma protein supplements.
This invention is illustrated with a specific glycosylated polypeptide comprising a human IL-2 mutein numbered in accordance with wild-type IL-2 wherein said human IL-2 is substituted at position 88 with arginine, whereby said mutein preferentially activates T cells over NK cells. The preferred mutein is designated IL-2N88R, using conventional terminology to describe the amino acid substitution of asparagine (N) with arginine (R) at position 88 of wild type IL-2. The nomenclature of the oligosaccharide structures is as described (Fukuda et al, 1994). Mammalian glycosylation patterns are well known and are described in Fukuda et al. (1994), incorporated herein by reference.
This mutein exhibits essentially wild-type IL-2 activity on T cells. This invention is also directed to a method of treating a patient afflicted with an IL-2 treatable condition by administering a therapeutically effective amount of a human IL-2 mutein numbered in accordance with wild-type IL-2 having PHA-blast activating activity but having reduced NK cell activating activity. This method is applicable wherein the IL-2 treatable condition is HIV, cancer, autoimmune disease, infectious disease, vaccine adjuvant in cancer vaccine and conventional vaccine therapy for immune stimulation in the elderly or otherwise immunocompromised, as well as in human SCID patients, or other therapeutic application requiring stimulation of the immune system.